This invention relates to apparatus for transmission of data from one instrument to another, and more specifically, to apparatus for transmission of knob setting data, such as range data, between electronic instruments.
In the prior art there are known measuring instruments which generate an analog voltage representative of the quantity being measured. However, in a number of such measuring instruments, measurement data may be provided over a number of ranges for the quantity being measured. One such device is a gas analyzer which provides but a single analog output for eight ranges of gas concentrations. That is, a variable voltage representing the measurement is provided but no indication is given as to the range in which the measurement was made.
In this type of gas analyzer, the output voltage which may be provided to indicate the measured quantity ranges from 0 to 5 volts DC, irrespective of the range of measurement. Thus, where the eight concentration ranges may cover (in parts per million) 0-5, 0-10, 0-20, 0-50, 0-100, 0-200, 0-500, and 0-1000, the provision of a specific output voltage alone is insufficient to identify the actual concentration measured by the analyzer since the same voltage may correspond to eight different measurements.
There is accordingly a need in the prior art to provide range information, corresponding to setting of a range selection knob for example, associated with data provided by an instrument.
There is a more generally expressed need in the prior art to provide information from one instrument to another indicative of a knob setting on the first instrument.
Although such needs may be satisfied by manual input of the range data (or knob setting position) to the receiving instrument, where the latter happens to be a computer, for example, such an approach leads to an increased potential for error, since an operator of the first instrument may forget to input a next range setting upon repositioning the control knob on the panel of the measuring instrument.
In order to provide an automatic transfer of range data from the measuring instrument to a computer, or other instrument, it is also possible to open the chassis of the measuring instrument in order to access the control switch for the range (or other knob) setting. However, this approach is complex, requires major modifications of the internal circuitry of the instrument, and may be physically difficult in the case of an instrument already cramped with electrical and mechanical connections.
There is thus a need for a simple, non-invasive structure for obtaining range data (or other knob setting data) in one instrument and for providing that data to another instrument.